This invention relates to friction braking systems and more particularly to aircraft friction discs with reinforced peripheral slots for use in multiple disc brakes.
In brake assemblies which employ a plurality of brake discs alternately splined to the wheel and axle of an aircraft, it is important to provide specially constructed drive means to reinforce peripheral slots in the discs to relieve the severe stressing that otherwise would rapidly deteriorate the periphery of the discs. When disc brakes were constructed of steel, the discs were able to withstand the shearing and compressive forces exerted thereon between the slots and the torque transmitting members because of their physical properties. With the replacement of the steel discs with carbon composition discs it was important to provide reinforcing inserts at the peripheral slots since the carbon composites have less strength than steel. The inserts transmit the forces to the carbon discs, over a larger area reducing the contact stresses which increases the load capability of the carbon composite discs.
Some friction discs with reinforced inserts at the slots do not adequately transfer the load. In some structures the load is transmitted via radially disposed pins to the carbon discs. These discs require precise machining for the placement of the radial holes while simultaneously weakening the discs due to the removal of substantial material along the entire radial wall. In some structures the inserts for the peripheral reinforced slots transmit the forces to the insert rivets and then to the openings in the disc through which the rivets extend. These openings accept all of the discs loading and are therefore subject to undesirable very high stress concentrations. The present invention utilizes an insert at the peripheral slots that engages the carbon disc and drives on the rotating member or transfers the stress to the stationary member without deleterious effects on the carbon composite materials . The insert has a pair of opposed faces which frictional contact the opposite walls of the slots to distribute the load. The insert design uses a channel to retain the inserts in position within the slot. Such structure eliminates peeling or fraying of the carbon composite heat sink material while also taking up some of the stresses due to misalignment in the wheel and brake. The structure of the insert and clip provides for a large bearing area in the carbon composite and minimizes the weight required to obtain the strength to handle the side loads in case of some misalignment. The construction permits the insert to float freely in the slot of the carbon disc thereby eliminating the tension loading of the attaching rivets.